Allow mysql_upgrade to enable event after table is corrected

new features:
set event_scheduler=ON|OFF will now try to init event scheduler
if it's not enabled
set event_scheduler=default will try to enable it based on
the value of the event_scheduler when mysqld was started

Author: montywi

client/mysql_upgrade.c

@@ -865,6 +865,7 @@ static const char *expected_errors[]=
   "ERROR 1060", /* Duplicate column name */
   "ERROR 1061", /* Duplicate key name */
   "ERROR 1054", /* Unknown column */
+  "ERROR 1290", /* RR_OPTION_PREVENTS_STATEMENT */
   0
 };
 

mysql-test/r/events_restart.result

@@ -18,7 +18,7 @@ change column body  body longtext character set utf8 collate utf8_bin;
 use events_test;
 select @@event_scheduler;
 @@event_scheduler
-DISABLED
+OFF
 show events;
 ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
 select event_name from information_schema.events;
@@ -40,12 +40,12 @@ ERROR HY000: Cannot proceed because system tables used by Event Scheduler were f
 drop event intact_check;
 ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
 set global event_scheduler=on;
-ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
+ERROR HY000: Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
 set global event_scheduler=off;
-ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
+ERROR HY000: Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
 show variables like 'event_scheduler';
 Variable_name	Value
-event_scheduler	DISABLED
+event_scheduler	OFF
 Make sure that we still can create and drop databases,
 and no warnings are produced.
 drop database if exists mysqltest_database_not_exists;
@@ -58,6 +58,22 @@ Error	1545	Failed to open mysql.event
 Restore the original mysql.event table
 drop table mysql.event;
 rename table event_like to mysql.event;
+check that we can now enable events without restart
+set global event_scheduler=original;
+Warnings:
+Note	1408	Event Scheduler: Loaded 3 events
+select @@global.event_scheduler;
+@@global.event_scheduler
+ON
+set global event_scheduler=on;
+select @@global.event_scheduler;
+@@global.event_scheduler
+ON
+show events;
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status	Originator	character_set_client	collation_connection	Database Collation
+events_test	abc1	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
+events_test	abc2	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
+events_test	abc3	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
 Now let's restart the server again
 use events_test;
 select @@event_scheduler;

mysql-test/r/mysql_upgrade-6984.result

@@ -57,3 +57,4 @@ Phase 6/6: Running 'FLUSH PRIVILEGES'
 OK
 update mysql.user set password='' where user='root';
 flush privileges;
+set global event_scheduler=OFF;

mysql-test/r/skip_grants.result

@@ -59,7 +59,9 @@ DROP FUNCTION f1;
 DROP FUNCTION f2;
 DROP FUNCTION f3;
 set global event_scheduler=1;
-ERROR HY000: The MariaDB server is running with the --event-scheduler=DISABLED or --skip-grant-tables option so it cannot execute this statement
+Warnings:
+Note	1408	Event Scheduler: Loaded 0 events
+set global event_scheduler=0;
 select count(*) from information_schema.COLUMN_PRIVILEGES;
 count(*)
 0

mysql-test/t/events_restart.test

@@ -71,9 +71,9 @@ drop event intact_check_1;
 drop event intact_check_2;
 --error ER_EVENTS_DB_ERROR
 drop event intact_check;
---error ER_EVENTS_DB_ERROR
+--error ER_STARTUP
 set global event_scheduler=on;
---error ER_EVENTS_DB_ERROR
+--error ER_STARTUP
 set global event_scheduler=off;
 show variables like 'event_scheduler';
 --echo Make sure that we still can create and drop databases,
@@ -84,6 +84,16 @@ drop database mysqltest_db1;
 --echo Restore the original mysql.event table
 drop table mysql.event;
 rename table event_like to mysql.event;
+
+--echo check that we can now enable events without restart
+set global event_scheduler=original;
+select @@global.event_scheduler;
+set global event_scheduler=on;
+select @@global.event_scheduler;
+--sorted_result
+--replace_column 6 # 9 # 10 #
+show events;
+
 --echo Now let's restart the server again
 
 --source include/restart_mysqld.inc

mysql-test/t/mysql_upgrade-6984.test

@@ -19,4 +19,5 @@ connect(con1,localhost,root,foo,,,);
 
 update mysql.user set password='' where user='root';
 flush privileges;
-
+# Load event table
+set global event_scheduler=OFF;

mysql-test/t/skip_grants.test

@@ -112,8 +112,8 @@ DROP FUNCTION f3;
 #
 # Bug #26807 "set global event_scheduler=1" and --skip-grant-tables crashes server
 #
---error ER_OPTION_PREVENTS_STATEMENT
 set global event_scheduler=1;
+set global event_scheduler=0;
 
 #
 # Bug#26285 Selecting information_schema crahes server

scripts/mysql_system_tables_fix.sql

@@ -597,6 +597,8 @@ ALTER TABLE event ADD body_utf8 longblob DEFAULT NULL
                       AFTER db_collation;
 ALTER TABLE event MODIFY body_utf8 longblob DEFAULT NULL;
 
+# Enable event scheduler if the event table was not up to date before.
+set global event_scheduler=original;
 
 #
 # TRIGGER privilege